Re: guile-user Digest, Vol 193, Issue 35

Re: guile-user Digest, Vol 193, Issue 35

[Daniel Llorens]

> From: Matt Wette <matt.wette@gmail.com>
> Subject: Re: Matrix or array operations library
> Date: 29 December 2018 at 00:24:38 CET
> To: guile-user@gnu.org
> 
> 
> On 12/28/18 12:23 PM, Daniel Llorens wrote:
>> 
>> John already wrote a nice explanation of how array strides work. You mean specifically for Guile?
>> 
>> 
> Yes, for Guile.  I understand strides and offsets.  I think the functionality is basically there
> with shared-arrays.  So I take back that Guile does not have this.  I will play later.
> 
> For example, interesting check will be if one can make a shared-1D array from the diagonal elements
> of a 2D square array (i.e., ((1 2 3) (4 5 6) (7 8 9)) => (1 5 9).

sure, I think that specific example is even in the manual. Yes, the 3rd example here

https://www.gnu.org/software/guile/manual/html_node/Shared-Arrays.html#index-make_002dshared_002darray

(transpose-array #2((1 2 3) (4 5 6) (7 8 9)) 0 0) also works; I've seen this idiom used in APL (say (0 0)⍉A).

> And the transpose I see as a utility that I guess just calls make-shared-array.

I think transpose-array happens to have a C implementation (although it could certainly be done using make-shared-array).

	Daniel